Taylor K A
International Livestock Research Institute, Nairobi, Kenya.
Int J Parasitol. 1998 Feb;28(2):219-40. doi: 10.1016/s0020-7519(97)00154-9.
Trypanosomosis in domestic livestock negatively impacts food production and economic growth in many parts of the world, particularly in sub-Saharan Africa. Current methods of control are inadequate to prevent the enormous annual socio-economic losses resulting from this disease. Hope for a vaccine based on the variant surface glycoprotein coat was abandoned several years ago when the complexity of the parasite's antigenic repertoire was appreciated. As a result, research is now focused on identifying invariant trypanosome components as potential targets for interrupting infection or infection-mediated disease. The identification of immune mechanisms involved in parasite and disease control, or conversely those responses that are associated with a poor clinical outcome, should facilitate the search for vaccine candidates and subsequent vaccine design strategies. To this end, comparative studies on the immune responses of trypanotolerant and trypanosusceptible breeds of cattle can be exploited. These studies have revealed that trypanotolerant and trypanosusceptible breeds of cattle have distinct antibody responses. Trypanosusceptible cattle produce high titres of polyspecific IgM but fail to produce IgG to specific trypanosome antigens. In contrast, although T cell and macrophage/monocyte responses of infected cattle are depressed, significant differences have not been described between tolerant and susceptible breeds of cattle. In this review, isotype-dependent effector mechanisms, such as complement activation, binding to Fc receptors, activation of phagocytic cells, neutralisation of parasite components, clearance of immune complexes and autoimmune responses, are discussed in the context of their potential impact on either susceptibility or tolerance of cattle to trypanosomosis. In addition, the links between specific cytokine patterns, macrophage/monocyte activation and depressed T cell responses that occur during trypanosome infection are presented. The identification of mechanisms that mediate depressed immune responses might suggest novel disease intervention strategies.
家畜锥虫病对世界许多地区，尤其是撒哈拉以南非洲地区的粮食生产和经济增长产生负面影响。目前的控制方法不足以预防这种疾病每年造成的巨大社会经济损失。几年前，当认识到寄生虫抗原库的复杂性后，基于变异表面糖蛋白外壳的疫苗研发希望破灭。因此，目前的研究重点是确定锥虫的不变成分，作为阻断感染或感染介导疾病的潜在靶点。确定参与寄生虫和疾病控制的免疫机制，或者相反，那些与不良临床结果相关的反应，应该有助于寻找候选疫苗和后续的疫苗设计策略。为此，可以利用对耐锥虫和易感染锥虫的牛品种免疫反应的比较研究。这些研究表明，耐锥虫和易感染锥虫的牛品种有不同的抗体反应。易感染锥虫的牛会产生高滴度的多特异性IgM，但不能产生针对特定锥虫抗原的IgG。相比之下，虽然感染牛的T细胞和巨噬细胞/单核细胞反应受到抑制，但耐锥虫和易感染锥虫的牛品种之间尚未发现显著差异。在这篇综述中，我们将在同型依赖性效应机制对牛对锥虫病易感性或耐受性的潜在影响的背景下，讨论补体激活、与Fc受体结合、吞噬细胞激活、寄生虫成分中和、免疫复合物清除和自身免疫反应等机制。此外，还介绍了锥虫感染期间特定细胞因子模式与巨噬细胞/单核细胞激活以及T细胞反应受抑制之间的联系。确定介导免疫反应受抑制的机制可能会提示新的疾病干预策略。
